Modalities to identify clinically actionable neoantigens.
TL;DR
Recent experimental platforms have been developed to validate neoantigen immunogenicity, which can be complemented by single-cell RNA/T-cell receptor sequencing to identify tumor-reactive T cell clones.
Abstract
Immune checkpoint inhibitors (ICIs), which restore antitumor immunity mediated by T cells, have caused a paradigm shift in cancer therapy. However, only a subset of patients achieve durable clinical responses, highlighting the need to better understand the mechanisms that determine antitumor immunity. Cancer-specific neoantigens are considered key determinants of effective immune responses because they are recognized as non-self by T cells and can induce strong immune responses. Accordingly, neoantigens are considered promising targets for cancer vaccines and adoptive cell therapies. Neoantigens have conventionally been considered to arise from somatic mutations and have been identified using whole-exome sequencing (WES). However, the number of neoantigens identified with WES remains limited. In contrast, advances in technology have revealed that peptides derived from various sources, including noncoding regions, are immunogenic and function as neoantigens. In particular, human leukocyte antigen (HLA) ligandome analyses, which enabled the direct identification of peptides presented on HLA molecules in combination with various sequencing technologies, have extended the landscape of neoantigen sources. However, in many cases, the immunogenicity of the identified neoantigen candidates has not been experimentally evaluated. Recently, several experimental platforms have been developed to validate neoantigen immunogenicity, which can be complemented by single-cell RNA/T-cell receptor sequencing to identify tumor-reactive T cell clones. In this review, we summarize current neoantigen identification strategies and discuss the challenges and future perspectives in neoantigen research.